dcache.c

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	check_lock();
	memcpy(dentry->d_iname, target->d_iname, DNAME_INLINE_LEN); 
	old_name = target->d_name.name;
	new_name = dentry->d_name.name;
	if (old_name == target->d_iname)
		old_name = dentry->d_iname;
	if (new_name == dentry->d_iname)
		new_name = target->d_iname;
	target->d_name.name = new_name;
	dentry->d_name.name = old_name;
}

/*
 * We cannibalize "target" when moving dentry on top of it,
 * because it's going to be thrown away anyway. We could be more
 * polite about it, though.
 *
 * This forceful removal will result in ugly /proc output if
 * somebody holds a file open that got deleted due to a rename.
 * We could be nicer about the deleted file, and let it show
 * up under the name it got deleted rather than the name that
 * deleted it.
 *
 * Careful with the hash switch. The hash switch depends on
 * the fact that any list-entry can be a head of the list.
 * Think about it.
 */
 
/**
 * d_move - move a dentry
 * @dentry: entry to move
 * @target: new dentry
 *
 * Update the dcache to reflect the move of a file name. Negative
 * dcache entries should not be moved in this way.
 */
  
void d_move(struct dentry * dentry, struct dentry * target)
{
	check_lock();

	if (!dentry->d_inode)
		printk(KERN_WARNING "VFS: moving negative dcache entry\n");

	spin_lock(&dcache_lock);
	/* Move the dentry to the target hash queue */
	list_del(&dentry->d_hash);
	list_add(&dentry->d_hash, &target->d_hash);

	/* Unhash the target: dput() will then get rid of it */
	list_del_init(&target->d_hash);

	list_del(&dentry->d_child);
	list_del(&target->d_child);

	/* Switch the parents and the names.. */
	switch_names(dentry, target);
	do_switch(dentry->d_parent, target->d_parent);
	do_switch(dentry->d_name.len, target->d_name.len);
	do_switch(dentry->d_name.hash, target->d_name.hash);

	/* And add them back to the (new) parent lists */
	list_add(&target->d_child, &target->d_parent->d_subdirs);
	list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
	spin_unlock(&dcache_lock);
}

/**
 * d_path - return the path of a dentry
 * @dentry: dentry to report
 * @vfsmnt: vfsmnt to which the dentry belongs
 * @root: root dentry
 * @rootmnt: vfsmnt to which the root dentry belongs
 * @buffer: buffer to return value in
 * @buflen: buffer length
 *
 * Convert a dentry into an ASCII path name. If the entry has been deleted
 * the string " (deleted)" is appended. Note that this is ambiguous. Returns
 * the buffer.
 *
 * "buflen" should be %PAGE_SIZE or more. Caller holds the dcache_lock.
 */
char * __d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
		struct dentry *root, struct vfsmount *rootmnt,
		char *buffer, int buflen)
{
	char * end = buffer+buflen;
	char * retval;
	int namelen;

	*--end = '\0';
	buflen--;
	if (!IS_ROOT(dentry) && list_empty(&dentry->d_hash)) {
		buflen -= 10;
		end -= 10;
		memcpy(end, " (deleted)", 10);
	}

	/* Get '/' right */
	retval = end-1;
	*retval = '/';

	for (;;) {
		struct dentry * parent;

		if (dentry == root && vfsmnt == rootmnt)
			break;
		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
			/* Global root? */
			if (vfsmnt->mnt_parent == vfsmnt)
				goto global_root;
			dentry = vfsmnt->mnt_mountpoint;
			vfsmnt = vfsmnt->mnt_parent;
			continue;
		}
		parent = dentry->d_parent;
		namelen = dentry->d_name.len;
		buflen -= namelen + 1;
		if (buflen < 0)
			break;
		end -= namelen;
		memcpy(end, dentry->d_name.name, namelen);
		*--end = '/';
		retval = end;
		dentry = parent;
	}
	return retval;
global_root:
	namelen = dentry->d_name.len;
	buflen -= namelen;
	if (buflen >= 0) {
		retval -= namelen-1;	/* hit the slash */
		memcpy(retval, dentry->d_name.name, namelen);
	}
	return retval;
}

/*
 * NOTE! The user-level library version returns a
 * character pointer. The kernel system call just
 * returns the length of the buffer filled (which
 * includes the ending '\0' character), or a negative
 * error value. So libc would do something like
 *
 *	char *getcwd(char * buf, size_t size)
 *	{
 *		int retval;
 *
 *		retval = sys_getcwd(buf, size);
 *		if (retval >= 0)
 *			return buf;
 *		errno = -retval;
 *		return NULL;
 *	}
 */
asmlinkage long sys_getcwd(char *buf, unsigned long size)
{
	int error;
	struct vfsmount *pwdmnt, *rootmnt;
	struct dentry *pwd, *root;
	char *page = (char *) __get_free_page(GFP_USER);

	if (!page)
		return -ENOMEM;

	read_lock(&current->fs->lock);
	pwdmnt = mntget(current->fs->pwdmnt);
	pwd = dget(current->fs->pwd);
	rootmnt = mntget(current->fs->rootmnt);
	root = dget(current->fs->root);
	read_unlock(&current->fs->lock);

	error = -ENOENT;
	/* Has the current directory has been unlinked? */
	spin_lock(&dcache_lock);
	if (pwd->d_parent == pwd || !list_empty(&pwd->d_hash)) {
		unsigned long len;
		char * cwd;

		cwd = __d_path(pwd, pwdmnt, root, rootmnt, page, PAGE_SIZE);
		spin_unlock(&dcache_lock);

		error = -ERANGE;
		len = PAGE_SIZE + page - cwd;
		if (len <= size) {
			error = len;
			if (copy_to_user(buf, cwd, len))
				error = -EFAULT;
		}
	} else
		spin_unlock(&dcache_lock);
	dput(pwd);
	mntput(pwdmnt);
	dput(root);
	mntput(rootmnt);
	free_page((unsigned long) page);
	return error;
}

/*
 * Test whether new_dentry is a subdirectory of old_dentry.
 *
 * Trivially implemented using the dcache structure
 */

/**
 * is_subdir - is new dentry a subdirectory of old_dentry
 * @new_dentry: new dentry
 * @old_dentry: old dentry
 *
 * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
 * Returns 0 otherwise.
 */
  
int is_subdir(struct dentry * new_dentry, struct dentry * old_dentry)
{
	int result;

	result = 0;
	for (;;) {
		if (new_dentry != old_dentry) {
			struct dentry * parent = new_dentry->d_parent;
			if (parent == new_dentry)
				break;
			new_dentry = parent;
			continue;
		}
		result = 1;
		break;
	}
	return result;
}

void d_genocide(struct dentry *root)
{
	struct dentry *this_parent = root;
	struct list_head *next;

	spin_lock(&dcache_lock);
repeat:
	next = this_parent->d_subdirs.next;
resume:
	while (next != &this_parent->d_subdirs) {
		struct list_head *tmp = next;
		struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
		next = tmp->next;
		if (d_unhashed(dentry)||!dentry->d_inode)
			continue;
		if (!list_empty(&dentry->d_subdirs)) {
			this_parent = dentry;
			goto repeat;
		}
		atomic_dec(&dentry->d_count);
	}
	if (this_parent != root) {
		next = this_parent->d_child.next; 
		atomic_dec(&this_parent->d_count);
		this_parent = this_parent->d_parent;
		goto resume;
	}
	spin_unlock(&dcache_lock);
}

/**
 * find_inode_number - check for dentry with name
 * @dir: directory to check
 * @name: Name to find.
 *
 * Check whether a dentry already exists for the given name,
 * and return the inode number if it has an inode. Otherwise
 * 0 is returned.
 *
 * This routine is used to post-process directory listings for
 * filesystems using synthetic inode numbers, and is necessary
 * to keep getcwd() working.
 */
 
ino_t find_inode_number(struct dentry *dir, struct qstr *name)
{
	struct dentry * dentry;
	ino_t ino = 0;

	/*
	 * Check for a fs-specific hash function. Note that we must
	 * calculate the standard hash first, as the d_op->d_hash()
	 * routine may choose to leave the hash value unchanged.
	 */
	name->hash = full_name_hash(name->name, name->len);
	if (dir->d_op && dir->d_op->d_hash)
	{
		if (dir->d_op->d_hash(dir, name) != 0)
			goto out;
	}

	dentry = d_lookup(dir, name);
	if (dentry)
	{
		if (dentry->d_inode)
			ino = dentry->d_inode->i_ino;
		dput(dentry);
	}
out:
	return ino;
}

static void __init dcache_init(unsigned long mempages)
{
	struct list_head *d;
	unsigned long order;
	unsigned int nr_hash;
	int i;

	/* 
	 * A constructor could be added for stable state like the lists,
	 * but it is probably not worth it because of the cache nature
	 * of the dcache. 
	 * If fragmentation is too bad then the SLAB_HWCACHE_ALIGN
	 * flag could be removed here, to hint to the allocator that
	 * it should not try to get multiple page regions.  
	 */
	dentry_cache = kmem_cache_create("dentry_cache",
					 sizeof(struct dentry),
					 0,
					 SLAB_HWCACHE_ALIGN,
					 NULL, NULL);
	if (!dentry_cache)
		panic("Cannot create dentry cache");

#if PAGE_SHIFT < 13
	mempages >>= (13 - PAGE_SHIFT);
#endif
	mempages *= sizeof(struct list_head);
	for (order = 0; ((1UL << order) << PAGE_SHIFT) < mempages; order++)
		;

	do {
		unsigned long tmp;

		nr_hash = (1UL << order) * PAGE_SIZE /
			sizeof(struct list_head);
		d_hash_mask = (nr_hash - 1);

		tmp = nr_hash;
		d_hash_shift = 0;
		while ((tmp >>= 1UL) != 0UL)
			d_hash_shift++;

		dentry_hashtable = (struct list_head *)
			__get_free_pages(GFP_ATOMIC, order);
	} while (dentry_hashtable == NULL && --order >= 0);

	printk("Dentry-cache hash table entries: %d (order: %ld, %ld bytes)\n",
			nr_hash, order, (PAGE_SIZE << order));

	if (!dentry_hashtable)
		panic("Failed to allocate dcache hash table\n");

	d = dentry_hashtable;
	i = nr_hash;
	do {
		INIT_LIST_HEAD(d);
		d++;
		i--;
	} while (i);
}

static void init_buffer_head(void * foo, kmem_cache_t * cachep, unsigned long flags)
{
	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
	    SLAB_CTOR_CONSTRUCTOR)
	{
		struct buffer_head * bh = (struct buffer_head *) foo;

		memset(bh, 0, sizeof(*bh));
		init_waitqueue_head(&bh->b_wait);
	}
}

/* SLAB cache for __getname() consumers */
kmem_cache_t *names_cachep;

/* SLAB cache for file structures */
kmem_cache_t *filp_cachep;

/* SLAB cache for dquot structures */
kmem_cache_t *dquot_cachep;

/* SLAB cache for buffer_head structures */
kmem_cache_t *bh_cachep;
EXPORT_SYMBOL(bh_cachep);

extern void bdev_cache_init(void);
extern void cdev_cache_init(void);

void __init vfs_caches_init(unsigned long mempages)
{
	bh_cachep = kmem_cache_create("buffer_head",
			sizeof(struct buffer_head), 0,
			SLAB_HWCACHE_ALIGN, init_buffer_head, NULL);
	if(!bh_cachep)
		panic("Cannot create buffer head SLAB cache");

	names_cachep = kmem_cache_create("names_cache", 
			PATH_MAX, 0, 
			SLAB_HWCACHE_ALIGN, NULL, NULL);
	if (!names_cachep)
		panic("Cannot create names SLAB cache");

	filp_cachep = kmem_cache_create("filp", 
			sizeof(struct file), 0,
			SLAB_HWCACHE_ALIGN, NULL, NULL);
	if(!filp_cachep)
		panic("Cannot create filp SLAB cache");

#if defined (CONFIG_QUOTA)
	dquot_cachep = kmem_cache_create("dquot", 
			sizeof(struct dquot), sizeof(unsigned long) * 4,
			SLAB_HWCACHE_ALIGN, NULL, NULL);
	if (!dquot_cachep)
		panic("Cannot create dquot SLAB cache");
#endif

	dcache_init(mempages);
	inode_init(mempages);
	mnt_init(mempages);
	bdev_cache_init();
	cdev_cache_init();
}